In an inflated and loaded condition, a radial tire is subject to bending moments at the sidewall areas at the center of the tire footprint. The strains and stresses created by the moments are directly related to the sidewall performance of the tire.
Previous research and studies have demonstrated that the maximum sidewall surface strain occurs in the least stiff area of the sidewall of a tire. Because of cord compression created during the loading of the tire, the combined cord tension in the upper sidewall area is reduced and that area is most vulnerable to sidewall bending. Therefore, the maximum sidewall surface strain is located in the upper sidewall area.